MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (SIX) WARNING NR 003// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 06W (SIX), LOCATED APPROXIMATELY 226 NM EAST- SOUTHEAST OF CHICHI JIMA, HAS TRACKED WESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS SITUATED WITHIN AN EXPOSED LOW-LEVEL CIRCULATION CENTER EVIDENT IN MULTISPECTRAL SATELLITE IMAGERY. THE INTENSITY OF 40 KNOTS IS BASED ON A CONSENSUS OF SUBJECTIVE DVORAK AND AUTOMATED INTENSITY ESTIMATES FROM MULTIPLE REPORTING AGENCIES. A 092248Z METOP-A ASCAT PASS INDICATES WINDS SPEEDS OF AT LEAST 30 TO 35 KNOT NEAR THE CENTER OF THE COMPACT SYSTEM. TS 06W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL STEERING RIDGE (STR) TO THE NORTH. THE SYSTEM IS PASSING OVER WARM WATER (29-30C) IN AN AREA OF MODERATE TO STRONG (20-25 KTS) VERTICAL WIND SHEAR (VWS). INCREASING EASTERLY VWS HAS LEFT THE LOW-LEVEL CIRCULATION PARTIALLY EXPOSED, AND CONFINED THE DEEPEST CONVECTION TO THE WESTERN PERIPHERY. HOWEVER, UPPER LEVEL OUTFLOW TOWARD A NARROW TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) TO THE WEST IS HELPING TO SUSTAIN THE SYSTEM IN THE PRESENCE OF THE INCREASING VWS. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 06W WILL CONTINUE TRACKING WESTWARD ALONG THE SOUTHERN EDGE OF THE STR. THE ENVIRONMENT WILL BECOME INCREASINGLY UNFAVORABLE AS VERTICAL WIND SHEAR INDUCED BY STRONG EASTERLY FLOW ALOFT PERSISTS. DESPITE THE PERSISTENT SHEAR, PASSAGE OVER WARM WATER AND A FAVORABLE OUTFLOW PATTERN IN THE NEAR-TERM SHOULD ALLOW THE SYSTEM TO REMAIN INTACT AS A WEAK TROPICAL STORM OR TROPICAL DEPRESSION THROUGH TAU 72. C. TS 06W IS EXPECTED TO FINALLY SUCCUMB TO INCREASING VWS AND DISSIPATE BY TAU 96. NUMERICAL MODEL SOLUTIONS REMAIN IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THE OVERALL JTWC FORECAST TRACK.// NNNN NNNN